Do microfilaments provide the motive force for the translocation and extrusion of beta granules?
The active role played by beta-cell microfilamentous structures in the dynamics of insulin secretion was investigated by examining the influence of cytochalasin B upon various parameters of hormonal release by the isolated perfused rat pancreas. The view that the cytochalasin-induced changes in insulin release are due to a primary biophysical effect on microfilaments, rather than to an unrelated biochemical alteration of the beta-cell glucose-sensor device, was strengthened by the following observations: (1) the onset and disappearance of the cytochalasin B-induced facilitating action upon insulin release followed a time-course parallel to that characterizing the ultrastructural changes provoked by the drug in the distribution of beta-cell microfilamentous material; and (2) cytochalasin B facilitated leucine-induced insulin release in the presence of a very low glucose concentration. The mold metabolite was also found to transform transient secretory responses into biphasic ones and to
